Papillary Thyroid Carcinoma Emerging from Hashimoto Thyroiditis Demonstrates Increased PD-L1 Expression, Which...

Area of Science:

• Immunology
• Oncology
• Pathology

Background:

• Programmed death-ligand 1 (PD-L1) expression is observed in thyroiditis but its role in papillary thyroid carcinoma (PTC) is unclear.
• Investigating PD-L1 in PTC is crucial for understanding thyroid cancer biology and potential therapeutic targets.

Purpose of the Study:

• To determine if background chronic lymphocytic thyroiditis (CLT) or Hashimoto thyroiditis (HT) affects PD-L1 expression in benign thyroid epithelium and PTC.
• To assess if PD-L1 expression in PTC is maintained in lymph node metastases.

Main Methods:

• Immunohistochemistry (IHC) was used to detect PD-L1 expression.
• Tissues analyzed included normal thyroid, CLT, HT, and PTC arising in these conditions.
• Lymph node metastases from PTC cases were also evaluated for PD-L1 expression.

Main Results:

• Increased PD-L1 expression (10-90%) was found in HT, minimal expression (1-5%) in some CLT cases, and no expression in normal thyroid.
• PTC arising in normal thyroid or CLT generally lacked PD-L1 expression.
• PTC arising in HT showed significant PD-L1 expression, which was retained in lymph node metastases. Background HT epithelium also expressed PD-L1.

Conclusions:

• Thyroid follicular epithelium in HT exhibits elevated PD-L1 expression.
• Papillary thyroid carcinoma developing in a background of HT demonstrates increased PD-L1 expression that persists with metastasis.